* Add third radio button to support cloud storage download preference
* Handle download preferences and UI states, while switching between three options
* Add method to check if provider is in use in Cloud Storage API
* Preferences cloud storage strings saved as resource url
* Updated old in-content with cloud storage pref UI changes
* Turn cloud storage API on/off using generic pref
MozReview-Commit-ID: AE3MlhgKp2C
61f830b1ba